The present application is related generally to large-bearing cage configurations, and in particular, to a large-bearing cage assembly, comprising of a plurality of discrete bridge elements coupled between axially-spaced cage wire rings which are adjacent opposite axial ends of the rolling elements.
The typical approach to large-bearing cage design has been to extend the design styles for smaller conventional bearings into the large bearing sizes. The first and most common attempt at meeting the needs of larger bearings used pin style cages to facilitate placement and retention of the rolling elements. While pin style cages provide excellent retention, they are heavy, complex, costly to assemble, block the flow of lubricant to critical wear surfaces, and cannot be disassembled without damaging either the cage rings or the cage pins.
Another approach is to modify a stamped-steel style cage for use in the large bearing size range. The first problem here is that for large bearing configurations, the cage designs become too large to be stamped or closed in, so alternate manufacturing processes, such as spun blanks that are water jet cut have been attempted. These alternative manufacturing processes seem to create more problems than they solve. The stamping problems for large size cages are eliminated, but at great cost. Cage costs are effectively increased, not lowered, by the use of alternative manufacturing processes. The step of closing-in is replaced by the steps of cutting the cage, adjusting the circumferential size to get appropriate clearance and welding the cage back together, a complex and costly process. Cage distortion, particularly in pocket length and location, as well as cage roundness and flatness, resulting from this manufacturing process can lead to bearing performance and roller retention issues if not controlled sufficiently. These types of cages are still relatively heavy, and are not easily serviceable. Typically, the resulting cage must be cut and re-welded when serviced.
Both the pin-style and formed cages require welding in close proximity to precision bearing components. There is therefore always a risk of bearing damage due to heat and welding spatter and debris.
Another alternate which has been tried is the use of segmented polymer cage structures as a more cost effective solution than the spun-blank water-jet cut steel cage, however, while polymer segmented cages have demonstrated the ability to perform satisfactorily in testing, they have potential limitations in scaling up to extremely large bearings. The polymer cages currently used in ultra large bearings market have all been made from polyether ether ketone (PEEK), a colorless organic polymer thermoplastic. For extremely large bearings the size and strength of the cage will need to be increased. The greater volume of PEEK required to make a sufficiently strong cage may become cost prohibitive.
An additional concern with any bearing assembly is a proper flow of lubrication to the critical wear surfaces on the bearing elements. A visual marking of rollers has been observed with water-jet cut steel cages and to a lesser extent with the polymer thermoplastic cages. Pin style cages have been known to have issues with pin wear or breakage due to lack of lubricant between the pin and roller. The large, rectangular section cage rings at each end of the rollers of the pin type may act to impede the circulation of grease in these lubrication systems. Likewise the flanges at each end of polymer segments in a polymer segmented cage, while acting to maintain grease within the roller complement, may affect the circulation of grease into and out of the complement. Alternate polymer segment flange designs can address this issue, but a significant flange is a basic requirement of the design of a polymer segmented cage
Accordingly, it would be advantageous to provide a segmented bearing cage or retainer assembly which offers the ability to retain very heavy sets of rollers in large bearing assemblies, which does not impede the flow of lubricant to the wear critical surfaces of the bearing assembly, and which is relatively low cost to manufacture.